It is known that hair in a desired form is obtained by conducting hair setting using a resin.
As resins for hair cosmetics having such a purpose, nonionic, anionic and cationic resins are employed.
Examples of the nonionic resin used for the hair cosmetics include polyvinyl methyl ether, polyvinyl pyrrolidone and the like. Polyvinyl pyrrolidone is susceptible to the influence of humidity conditions. Described specifically, before moisture absorption, its film is hard and tends to cause a flaking phenomenon, while under high-temperature and high-humidity conditions, it becomes extremely flexible and causes a blocking phenomenon. There is therefore a potential danger that hairs stick to each other and it becomes impossible to comb or brush them. Polyvinyl methyl ether is much more susceptible to humidity.
Examples of the anionic resin include copolymers of a vinylcarboxylic acid, as an ionic group, such as acrylic acid and methacrylic acid with styrene, an alkyl acrylate or the like. Different from the nonionic resin, the anionic resin is less influenced by humidity, but because having an anionic property similar to hair, its affinity for hair is weak. In addition, the film of the anionic resin is fragile in spite of being hard and having high hair-conditioning effects so that there is a potential danger of occurring a flaking phenomenon. Moreover, the use of an anionic resin restricts the addition of a cationic substance, thereby possibly causing a solidifying phenomenon when a hair rinse (cationic-base) is used at the time of hair washing.
The cationic resin has a stronger affinity for hair than the former two resins, but is susceptible to humidity as in the nonionic resin. In addition, it is accompanied with the problems such as fears of toxicity and irritation to skin resulting from its cationic property, a limitation to the addition of the anionic resin and a solidifying phenomenon at the time when a shampoo (anionic-base) is used upon hair washing.
There is increasingly a demand for a hair cosmetic composition which can be removed easily by washing of the hair, can be readily diluted with water upon its preparation, and is free from an alcohol content in view of an environmental problem. It is therefore preferred that the resin to be employed is water soluble. In general, an increase in the water solubility of the resin, however, leads to a problem that the setting force lowers.
As a hair cosmetic composition which overcomes the defects of those containing the anionic resin, cationic resin or nonionic resin, an amphoteric ion polymer, that is, a copolymer containing as a hydrophilic group a carboxybetaine fracture has been proposed. The amphoteric ion polymer is known as a hair conditioning polymer excellent in performances such as affinity for hair and setting force. The amphoteric ion polymer proposed is a hair conditioning resin composed of an amphoteric polymer obtained by converting into, a corresponding amphoteric polymer, a terpolymer of (a) a tertiary-amine-containing (meth)acrylate (the term "(meth)acrylic acid" will hereinafter embrace both acrylic acid and methacrylic acid) base unsaturated monomer, (b) a C.sub.1-4 alkyl (meth)acrylate and (c) a C.sub.12-18 alkyl (meth)acrylate, with a halogenated acetate (refer to JP-A-51-9732 and JP-A-55-104209) (the term "JP-A" as used herein means an "unexamined published Japanese patent application").
However, the above amphoteric ion polymer has not a sufficient compatibility with various cosmetic base materials, for example, an anionic surfactant. Particularly, it is inferior in compatibility with a base material for gel.
As described above, the conventional resins cannot always satisfy all the performances.